Zk-SNARK stands for “Zero-Knowledge Succinct Non-Interactive Argument of Knowledge.” It is cryptographic proof that allows one party to prove it possesses certain information without revealing that information. First developed from zero-knowledge proofs in the 1980s, Zk-SNARK is now used in cryptocurrencies to enhance privacy, most notably in Zcash, where it hides transaction details unlike Bitcoin's transparent ledger. Recent upgrades, such as Halo 2, have further strengthened this trustless privacy model.